Make bundle options visible to installer

Bundle configuration options that are inferred from the bundle specs
overwrite user provided ones. This used to prevent users from changing
the name of directory where the cloned bundle should go, for instance.

Keep the user provided options with a preference over inferred ones.

autoload/vundle/config.vim

@@ -27,7 +27,7 @@ func! vundle#config#init_bundle(name, opts)
   if a:name != substitute(a:name, '^\s*\(.\{-}\)\s*$', '\1', '')
     echo "Spurious leading and/or trailing whitespace found in bundle spec '" . a:name . "'"
   endif
-  let opts = extend(s:parse_options(a:opts), s:parse_name(substitute(a:name,"['".'"]\+','','g')))
+  let opts = extend(s:parse_options(a:opts), s:parse_name(substitute(a:name,"['".'"]\+','','g')), 'keep')
   let b = extend(opts, copy(s:bundle))
   let b.rtpath = s:rtpath(opts)
   return b